In fluidization processes particulate solids are maintained in a percolating or ebullating state by air or other process gas distributed evenly over the bottom of the fluidized bed chamber. Such chambers are utilized in a variety of processes including combustion, reaction, mixing and heat transfer applications. A wide range of processing environments can be encountered, specifically high temperature, erosive and corrosive conditions.
Prior art distributors include perforated plates, spargers and perforated plates with covers or bubble caps placed atop the perforations. Each of these distributors is in direct contact with the processing environment, and is subjected not only to temperature and corrosion, but also to erosion by solids during operation of the process. Perforated plates do not have internal surfaces as do bubble cap plates and spargers, and, thus, are the least expensive to fabricate, install and maintain. However, when the fluidization gas flow is stopped, the fluidized particulate solids settle onto the perforated plate, said plate allowing particulate solids to filter or sift through said perforations thereby subjecting the lower portions of the fluidization vessel to the temperature and possibly corrosive conditions in the fluidization chamber. Furthermore, filtered solids must be removed and returned to the bed chamber to reduce loss and prevent maloperation on start-up.
Bubble cap plates and spargers prevent this downward solids filtering, but are immersed in the solids during operation and must be fabricated from materials that can withstand the processing environment. Typically, replacement of the sparger or caps is required on a regular basis.